Vacuum Modulator
- Disconnect vacuum hoses from both ports of vacuum modulator. Plug port nearest EGR valve and blow air into port farthest from EGR valve. Air should escape freely through air filter of modulator.
- Start engine and maintain engine speed at 3000 RPM. Repeat blow test. There should be strong resistance to air flow. If not, replace vacuum modulator. Reconnect vacuum hoses to proper locations.